There has recently been a growing need for microminiaturization of electronic wiring following the trend towards higher definition of displays and miniaturization or higher densification of electronic components. A method of manufacturing a conductive pattern used in electronic wiring using a resin composition containing conductive particles is generally a method in which a pattern is formed on a substrate and conductive particles are brought into contact with each other by firing under heating to obtain a conductive pattern. The method of forming a pattern on a substrate includes, for example, a screen printing method, an ink jet method or a photolithographic method and it is considered that the screen printing method and the ink jet method are not suited for formation of a fine pattern and the photolithographic method is suited for formation of a fine pattern.
The photolithographic method is a method in which, after coating and drying a photosensitive composition, the coating film thus obtained is irradiated with ultraviolet rays through a photomask having a fine wiring pattern shape drawn thereon to form the exposed area and the unexposed area on the coating film, and development with a developing solution is performed to form a fine pattern on a substrate, and then a fine conductive pattern is formed by the subsequent electroconductive treatment. The photosensitive composition used in that method is composed of conductive particles, a photosensitizer, a resin and the like (Japanese Unexamined Patent Publication (Kokai) No. 2000-199954).
To form an ultrafine pattern in size of 5 μm or less, there is a need to use, as conductive particles, particles having a smaller particle diameter called metal fine particles. In that case, from the viewpoint of surface smoothness and side face linearity of the pattern, it is necessary to use fine particles having a particle diameter sufficiently smaller than the wiring width required. As a result, mobility of atoms on the surface noticeably increases in fine particle and, when the particles are brought into contact with each other, fusion is likely to occur, thus advantageously serving the purpose of realizing the process at lower temperature.
However, fusion of metal fine particles proceeds even at around room temperature and a composition prepared by using particles having a particle diameter, which is likely to cause fusion, may sometimes cause deterioration of coatability or photosensitivity due to the existence of fused particles having a large size. To prevent that problem, surface coating of various metal fine particles is performed for the purpose of preventing fusion by suppressing contact between metal fine particles.
Coating of metal fine particles with an organic substance in a liquid phase has popularly performed as the method for surface coating and, for example, there have been known silver fine particles whose surfaces are coated with an amine compound (Japanese Unexamined Patent Publication (Kokai) No. 2006-219693 and Japanese Unexamined Patent Publication (Kokai) No. 2008-034358), silver fine particles whose surfaces are coated by a vapor phase reaction method (Japanese Unexamined Patent Publication (Kokai) No. 2013-196997) and the like.
However, if conductive particles are introduced in the amount required to exhibit conductivity after a heat treatment, it is impossible to sufficiently ensure a photosensitizer and a resin required to exhibit photosensitivity, leading to drastic deterioration of patterning property, thus failing to form a fine conductive pattern. Meanwhile, if a photosensitizer and a resin are introduced in the amount required to exhibit photosensitivity, it is impossible to exhibit conductivity after a heat treatment, although satisfactory patterning property is achieved.
It could therefore be helpful to provide a photosensitive resin composition that can achieve both resolution of a fine pattern and conductivity after heat treatment. Use of such photosensitive resin composition enables formation of a high resolution conductive pattern.